A motion guide device of this type is provided with a track member attached to a fixed portion, and a moving member fixed to a movable portion. The moving member is assembled to the track member in a rectilinearly movable manner. Between the track member and the moving member, many rollers for reducing frictional resistance are interposed being capable of making a rolling motion. A circuit-like endless circulating path on which the rollers circulate is provided to the moving member. The circuit-like endless circulating path of the motion guide device is constituted of an unloaded rolling element rolling path that is parallel to a loaded rolling element rolling path between a rolling element rolling surface of the track member and a loaded rolling element rolling surface of the moving member, and a pair of U-shaped direction change paths that connects the loaded rolling element rolling path with the unloaded rolling element rolling path (see Patent Literature 1 below).
In the endless circulating path, many rollers are arranged and housed. Many rollers are rotatably held by a roller retainer. The roller retainer is provided with many spacers interposed between the rollers in the front and back in a travelling direction, and a belt portion coupling the spacers together. The spacer is interposed between the rollers in the front and back in the travelling direction to prevent the rollers in the front and back in the travelling direction from coming in sliding contact with each other. In addition, it is possible to make assembly of the roller retainer easy by coupling many spacers together using the belt portion. Furthermore, by using this roller retainer, it is configured to prevent skew of the rollers. In addition, a roller retainer belt guide groove that guides the belt portion is provided to the unloaded rolling element rolling path and the direction change path, whereby the belt portion guides the rollers on an unloaded circulation path.